Fuse device

ABSTRACT

A fuse device with a conducting strain wire structure connected at the opposite ends thereof to spaced terminals and intermediate the ends thereof to an indicator to hold the indicator in an operative position until the fuse device blows whereupon the strain wire structure fuses to release the indicator which then moves to an indicating position.

United States Patent Wilson [4 1 Apr. 18, 1972 [54] FUSE DEVICE 3,134,874 5/1964 Cameron ..337/l58 X [72] Inventor: James C. Wilson, Beaver, Pa. I FOREIGN PATENTS OR APPLICATONS [731 Assign wesfinghwse Electric W 1,465,397 1/1967 France ..337/244 sburgh, Pa.

[22] Filed; Aug. 31, 1970 Primary Examiner-Bernard A. Gilheany Assistant Examiner-F. E. Bell [21] APPLNOJ 68,222 Attorney-A. T. Stratton, Clement L. Mcl-lale and W. A.

' Elchik [5,2} U.S. Cl ..337/244, 337/158 51 Int. Cl. ..H01h 85/30 ABSTRACT [58] held of Search A fuse device with a conducting strain wire structure connected at the opposite ends thereof to spaced terminals and in- 56] R fer Ce C1 d termediate the ends thereof to an indicator to hold the indicae en S H tor in an operative position until the fuse device blows UNITED STATES PATENTS whereupon the strain wire structure fuses to release the indicator which then moves to an indicating position. 3,319,027 5/1967 Hitchcock ..337/244 UX 2,914,636 11/1959 Kozacka ..337/158 X 3 Claims, 5 Drawing Figures 3 Sheets-Sheet 1 1 FUSE DEVICE CROSS-REFERENCE TO RELATED APPLICATIONS 752,848 filed Aug. 15, 1968;

BACKGROUND OF THE INVENTION l. Field of the Invention Fuse devices ofthe type comprising indicating means for indicating when the fuse is in a blown condition.

2. Description of the Prior Art In the patent to A. J. Fister, US. Pat. No. 3,281,555, there is disclosed a fuse device with a 'vertically extending strain wire that is connected at its lower end to a separate conductor that is fixedly held to an insulating supporting plate and electrically connected to one of the fuse terminals. The vertically extending strain wire is connected at its upper end to an indicator. The strain wire is also connected at its upper end to a separate conductor that is in turn electrically connected to a helical spring that is in turn in electrical contact with a cupshaped housing that is in turn electrically connected to another conductor that is connected to the other fuse terminal. When the fuse blows the current is transferred to the current path through the strain wire which then fuses to release the indicator that then moves to an indicating position.

SUMMARY OF THE INVENTION A fuse device comprises an insulating housing and a pair of terminal parts supported in the housing in a spaced relationship. Conducting fusible-element means is connected between the spaced terminal parts to electrically connect the spaced terminal parts. A conducting strain wire structure is connected at one end thereof directly to afirst of the terminal parts and at the other end thereof directly to the second of the terminal parts. The insulating housing is provided with an opening at the front thereof, and an indicator is disposed within the housing at the opening. A coil spring is mounted under the indicator to bias the indicator from an inoperative position toward an indicating position. The conducting strain wire structure is twisted intermediate the ends thereof in proximity to the front of the insulating housing, and the conducting strain wire structure is connected to. the indicator above the twisted portion thereof. The opposite ends of the conducting strain wire structure are connected to the terminal parts in proximity to the back of the insulatinghousing. The insulating housing is filled with an arc-quenching filler materiaL-such as sand, which is disposed throughout the housing except for a tubular cavity that houses the indicator and the biasing means for the indicator. The conducting strain wire structure has a greater resistance than the fusible element means so that under normal current conditions the current is conducted BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view, with parts broken away, of a fuse device constructed in accordance with principles of this inventron;

FIG. 2 is a sectional view taken generally along the lines II- II of FIG. 1;

FIG. 3 is an exploded side view, with parts broken away, of the fuse device seen in FIGS. 1 and 2;

FIG. 4 is an end view of the parts of FIG. 3 looking in the direction of the IV-IV arrows of FIG. 3; and

FIG. 5 is a perspective view of the gasket seen in FIGS. 2-4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is disclosed, in FIGS. 1-4, a fuse device3. Except for the construction and arrangement of the strain wire structure, the fuse device 3 is of similar construction to the fuse device disclosed in the copending patent application of James C. Wilson, Ser. No. 752,848, filed Aug. 15, 1968. The fuse device 3 of the instant invention may be used in conjunction with a circuit breaker in the same manner as is disclosed in the above-mentioned copending application Ser. No. 752,848. The fuse device 3 is a three-pole fuse device comprising an insulating housing indicated generally at 5. The housing 5 comprises an insulating front housing part 7 and an insulating back housing part 9. The front housing part 7 is molded with insulating barrier means to form three adjacent compartments 11 (FIG. 3). A separate fuse means indicated generally at 13 is supported in each of the compartments 11.

Each of the fuse means 13 (FIGS. 3 and 4) comprises a pair of terminals 15 and 17. Each of the terminals 15 comprises an internal generally planar terminal part 19 that is bent over at the lower. end thereof to provide an external generally planar terminal part 21 that extends generally normal to the plane of the associated tenninal part 19. Each of the terminals 17 com prises an internal generally planar terminal part 23 that is bent over at the lower end thereof to provide an external generally planar terminal part 25 that extends generally normal to the plane of the associated terminal part 23. Each of the internal terminal parts 19, 23 is provided with a plurality of recesses on the inside flat face thereof, and a plurality of metallic fusible elements 27 are supported on the inside faces of the terminal parts 19,23. Each of the fusible elements 27 is positioned at the opposite ends thereof in the recesses in the terminal parts 19, 23, and the ends are soldered into position to fixedly support each element on the inside faces of the terminal parts 19, 23. As can be understood with reference to FIGS. 2 and 3, there are two rows of fusible elements 27 between each pair of terminal parts 19, 23 with each row comprising three fusible elements 27'that are slanted to provided elongation of the fusible elements 27 within the space between the faces of the terminal parts 19, 23. As can be seen in FIGS. 2 and 3, one row between the terminal parts by means of the fusible element means. Upon the occurrence of an overload above a predetermined value the fusible element means fuses transferring the current to the conducting strain wire structure which then fuses to release the indicator which biases the indicator through the opening at the front of the'housing to provide an external visual indication that the fuse has blown. An advantage of the present invention is that the current path of the conducting strain wire structure is totally immersed in the -the fuse device.

comprises three parallel fusible elements 27 slanted in one direction and the other row comprises three parallel fusible elements 27 slanted in another direction. Each of the fusible elements 27 is provided with a plurality of slots at the opposite sides thereof to provide a plurality of portions of reduced cross-section that will fuse or blow upon the occurrence of overload current conditions. A pair of rigid insulating supporting and spacing members 29, 31 are provided between each pair of terminals 15, 17 to support and space the terminals l5, 17 in the manner disclosed in FIGS. 2 and 3. As can be seen in FIGS. l-3, each of the terminals l5, I7 is provided with a slot at the upper end thereof, and the upper rigid insulating supporting and spacing member 31 is provided with a pair of projections that are positioned within the slots to position the supporting and spacing member 31. Each of the terminals 15, I7 is provided with a notch at the lower end thereof, and the lower insulating supporting and spacing member 29 is provided withprojections that engage in the notches to position the lower insulating supporting and spacing member 29. A conducting fusible strain wire structure 35 is connected at the opposite ends thereof to the terminals 15, 17. The conducting fusible strain wire structure 35 is connected intermediate the ends thereof to an indicator 37 in a manner to be hereinafter more specifically described. The insulating housing is provided with an opening 39 at the front thereof for each of the indicators 37, and each of the indicators 37 is disposed at the associated opening 39. Each of the indicators 37 is positioned in an insulating tube 41. An insulating gasket 43 is provided at the upper end of each tube 41 between the tube 41 and a stop surface of the insulating housing 5. An insulating gasket 45 is positioned at the bottom of each of the tubes 41 between the tube 41 and the insulating support and spacing member 31. The gasket 45 is provided with a small opening therein through which the strain wire structure 35 extends. A coil compression spring 47 is provided in each of the tubes 41 to bias the associated indicator 37 frontward from the inoperative position seen in FIG. 2 toward an indicating position. When the indicator 37 is released, the associated spring 47 biases the indicator frontward, and a stop surface 49 on the indicator 37 limits frontward movement by engaging the associated gasket 43 in the indicating position wherein the front of the indicator 37 protrudes from the housing through the opening 39.

As can be understood with reference to FIG. 3, lateral movement of the insulating supporting and spacing members 29, 31 is prevented by the positioning of the members 29, 31 in the notches in the terminals 15, 17. The external terminal part 21 (on the left as seen in FIG. 2) is provided with an opening therein, and a solderless terminal connector 51 is connected to the terminal part 21 by means of a screw 53 that extends through the opening in the terminal part 21 and is threaded into a tapped opening in the solderless terminal connector 51. The external terminal part 25 seen on the right in FIGS. 2 and 3 is provided with an opening therein, and a bolt 55 extends through the opening to receive a nut 57 at the lower end thereof, which bolt and nut 55, 57 enable connection of the terminal part 25 to a terminal of, for example, a circuit breaker.

As will be understood with reference to FIG. 3, there is a slot 59 at one end of each of the compartments 11 of the front housing part 7, and a cavity 61 opposite each slot 59. There is a slot 63 at the back of the front housing part 7 at the opposite end of each of the compartments 11. When it is desired to assemble the fuse device 3, the front housing part 7 is turned over, and each of the assembled fuse means 13 is then dropped downward into the associated compartment 11. Each of the fuse means 13 is dropped in place as an assembled structure. Inward movement of each of the fuse means 13 is limited when the front portions of the terminal parts 21, 25 engage insulating surfaces at the slots 59, 63. During movement of each of the fuse means 13 into position, the associated solderless terminal connector 51 moves into the associated cavity 61. After the three fuse means 13 are properly positioned in the associated compartments, a resilient gasket 67 (FIG. 5) is placed on the housing part 7 and an arc-quenching filler material 71 (FIGS. 1 and 2), such as sand, is poured into the compartments 11 to fill the voids in the compartments. With the fuse means 13, filler material 71 and gasket 67 in position the lower housing part 9 is placed into position against the gasket 67 and the housing parts 7, 9 are then secured together by means of four bolts-73 and four nuts 75. The gasket 67 serves to prevent the escape of filler material from the housing. The gaskets 43, 45 prevent the entrance of filler material into the inside of the tubes 41-. When the housing parts 7, 9 are secured together the fuse device is turned over to the upright position seen in FIG. 2. In the upright position, the lower surfaces of the legs 21, 25 rest on the gasket 67 that is positioned on the flat front surface of the lower housing part 9 to thereby support the three fuse means 13 on the front housing part 9. Thereafter, the small openings between the front portions and sides of the terminal parts 21, 25 at the peripheries of the openings of the slots 59, 63 are sealed by means of an insulating cement that is painted into these openings. The cement is a type of cement that may be painted into position to take a firm set without actually getting hard so that if relative movement of the fuse means 13 occurs the cement will not crack. The cement serves to prevent the escape of the filler material through the openings through which the terminal parts 21, 25 extend.

The indicator 37 (FIG. 3) is provided with an opening 79 that is counterbored to provide a shoulder surface within the opening. The strain wire structure 35 is an elongated single wire that is twisted intermediate the ends thereof to provide the twisted portion 81. The upper part of the strain wire structure 35, above the twisted portion 81, is folded over twice and dipped in hot solder to provide a lump portion 83. During assembly of the fuse means 13, the free ends of the strain wire structure 35 are passed down through the opening 79 in the indicator 37 until the lump portion 83 engages against the shoulder surface within the opening 79. The coil spring 47 is moved over the free ends of the strain wire structure 35, and the free ends of the strain wire structure 35 are moved down through an opening, which is a very small opening, in the gasket 45 to thereby assemble the gasket 45, spring 47 and indicator 37. The free ends of the strain wire structure 35 are then moved down through an opening in the insulating support member 31, and the tube '41 and 43 are then mounted over top of the indicator and coil spring as is shown in FIG. 2. The strain wire structure 35 is pulled down to compress the biasing spring 47 pulling the indicator 37 down to the position shown in FIG. 1 within the tube 41, and the opposite ends of the strain wire structure 35 are soldered to the terminals 15, 17 at the lower ends of the terminals 15, 17. The fuse assembly 13 is then mounted in the housing 5 in the manner that was hereinbefore described with the filler material 71 filling the voids in the compartments 11.

The conducting strain wire structure 35 is made of copper and the fusible elements 27 are made of silver. The cross-section of the strain wire 35 is 159 circular mills and the crosssection of the reduced portions of each of the fusible elements 27 is 520 circular mills. With the cross-section of the strain wire 35 being substantially less than the cross-section of the fusible elements at their reduced portions and with the length of the strain wire 35 being substantially more than the length of the fusible elements 27, current between'the terminals 15, 17 will normally be carried by the fusible elements 27. Upon the occurrence of an overload above a predetermined value, the fusible elements 27 will fuse and the current will be instantaneously transferred to the strain wire structure 35 which will then instantaneously fuse releasing the indicator 37 whereupon the biasing spring 47 will bias the indicator 37 frontward from the inoperative position seen in FIG. 2 to an indicating position wherein the top of the indicator 37 protrudes extends frontward from the top of the housing 5 to thereby provide a visual indication that the fuse has blown. Movement of the indicator 37 to the indicating position is limited by the engagement of the shoulder portion 49 of the indicator 37 with the gasket 43.

As can be understood with reference to FIG. 2, the strain wire structure 35 is connected at the opposite ends thereof to the terminals 15, 17 at the back portions of the terminals 15, 17 and the strain wire structure 35 extends frontward where it is connected, intermediate the ends thereof, to the indicator 37. The twisted portion 81 of the strain wire structure 35 provides that the current path through the strain wire structure 35 is fully within the tiller material 71 so that the strain wire structure 35 will fuse within the filler material 71 rather than within the air space of the tube 41. The strain wire structure 35 is relatively simple in construction and easy to assemble during manufacture of the fuse device 5.

Iclaim:

1. A fuse device comprising an insulating housing forming a compartment, a pair of terminal parts supported in said compartment in a spaced relationship, said terminal parts being supported opposite each other with each terminal part extending from back-to-front in said housing, conducting fusible-element means between said spaced terminal parts electrically connecting said spaced terminal parts, a conducting strain wire structure connected at one end thereof to a first of said terminal parts in proximity to the back of said first terminal part and at the other end thereof to the second of said terminal parts in proximity to the back of said second terminal part, an indicator positioned in proximity to the front of said compartment, resilient biasing means biasing said indicator from an inoperative position toward an indicating position, said compartment being substantially filled with an arc-quenching filler material, said strain wire structure intermediate the ends thereof comprising a current path portion and an extension, said strain wire structure comprising a portion twisted together intermediate the ends thereof to provide said current path portion in said arc-quenching filler material with said extension being above said current path portion, an enclosure in said compartment enclosing said indicator said biasing means and said extension keeping said arc-quenching filler material away from said indicator said biasing means and said extension, said extension being connected to said indicator in proximity to the front of said compartment to hold said indicator in said inoperative position against the bias of said biasing means, said strain wire structure having an electrical resistance greater than the electrical resistance of said fusibleelement means whereby under normal current conditions the current from said first terminal part to said second terminal part is carried substantially through said fusible-element means, upon the occurrence of overload current conditions above a predetermined value said fusible-element means fusing and transferring current to said strain wire structure which then fuses to release said indicator whereupon said biasing means biases said indicator to said indicating position, and the current path through said strain wire structure extending through said current path portion all of which current path is within said arc-quenching filler material.

2. A fuse device according to claim 1, said strain wire structure at a first end thereof being connected directly to said first terminal part and at the second end thereof being connected directly to said second terminal part.

3. A fuse device according to claim 2, an insulating supporting and spacing member in proximity to the front of said terminal parts supporting and spacing said terminal parts, said insulating supporting and spacing member having an opening therein, said twisted portion of said strain wire structure being disposed below said opening with said strain wire structure extending through said opening to provide said extension above said insulating and supporting member which extension is connected to said indicator above said insulating supporting and spacing member, said enclosure being supported above said insulating supporting and spacing member enclosing said indicator said biasing means and said extension above said insulating supporting and spacing member. 

1. A fuse device comprising an insulating housing forming a compartment, a pair of terminal parts supported in said compartment in a spaced relationship, said terminal parts being supported opposite each other with each terminal part extending from back-to-front in said housing, conducting fusible-element means between said spaced terminal parts electrically connecting said spaced terminal parts, a conducting strain wire structure connected at one end thereof to a first of said terminal parts in proximity to the back of said first terminal part and at the other end thereof to the second of said terminal parts in proximity to the back of said second terminal part, an indicator positioned in proximity to the front of said compartment, resilient biasing means biasing said indicator from an inoperative position toward an indicating position, said compartment being substantially filled with an arc-quenching filler material, said strain wire structure intermediate the ends thereof comprising a current path portion and an extension, said strain wire structure comprising a portion twisted together intermediate the ends thereof to provide said current path portion in said arc-quenching filler material with said extension being above said current path portion, an enclosure in said compartment enclosing said indicator said biasing means and said extension keeping said arc-quenching filler material away from said indicator said biasing means and said extension, said extension being connected to said indicator in proximity to the front of said compartment to hold said indicator in said inoperative position against the bias of said biasing means, said strain wire structure having an electrical resistance greater than the electrical resistance of said fusible-element means whereby under normal current conditions the current from said first terminal part to said second terminal part is carried substantially through said fusible-element means, upon the occurrence of overload current conditions above a predetermined value said fusible-element means fusing and transferring current to said strain wire structure which then fuses to release said indicator whereupon said biasing means biases said indicator to said indicating position, and the current path through said strain wire structure extending through said current path portion all of which current path is within said arc-quenching filler material.
 2. A fuse device according to claim 1, said strain wire structure at a first end thereof being connected directly to said first terminal part and at the second end thereof being connected directly to said second terminal part.
 3. A fuse device according to claim 2, an insulating supporting and spacing member in proximity to the front of said terminal parts supporting and spacing said terminal parts, said insulating supporting and spacing member having an opening therein, said twisted portion of said strain wire structure being disposed below said opening with said strain wire structure extending through said opening to provide said extension above said insulating and supporting member which extension is connected to said indicator above said insulating supporting and spacing member, said enclosure being supported above said insulating supporting and spacing member enclosing said indicator said biasing means and said extension above said insulating supporting and spacing member. 